Structural transformations of carbon nanotubes under hydrostatic pressure.

We used simulations with a classical force field to study the transformation under hydrostatic pressure of isolated single-walled nanotubes (SWNT) from a circular to a collapsed cross section. Small-diameter SWNTs deform continuously under pressure, whereas larger-diameter SWNTs display hysteresis and undergo a first-order-like transformation. The different behavior is due to the changing proportions in the total energy of the wall-curvature energy and the van der Waals attraction between opposite walls of the tube.